• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.25-28
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• 2000

In this study, Transient Characteristics of the Punch-Through Insulated Gate Bipolar Transistor (PT-IGBT) has been studied. On the contraty to Non-Punch Through Insulated Gate Bipolar Transistor(NPT-IGBT), PT-IGBT has buffer layer It has a simple drive circuit controlled by the gate voltage of the MOSFET and the low on-state resistance of the bipolar junction transistor. In this paper, the transient characteristics with temperature of the PT-IGBT has been analyzed analytically. PT-IGBT is made to reduce switching power loss. Excess Minority carrier distribution inactive base region and base charge, the rate of voltage with time is expressed analytically to include buffer layer.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1358-1360
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• 2005

본 논문에서는 비접촉 전원장치와 같이 누설인덕턴스가 큰 공진형 컨버터에서 스위치단과 공진 탱크 사이에 강압형 매칭 트랜스포머를 삽입하여 스위치의 공진 전류를 줄이는 방법을 제안하였다. 누설인덕턴스가 큰 공진형 컨버터에 강압형 매칭 트랜스포머를 추가함으로써, 일차측의 입력 임피던스를 증가시켜 동일 전압에 대하여 전류의 크기를 작게 하고, 또한 전압과 전류의 위상을 거의 일치시켜 무효 전력 성분을 감소시킬 수 있다. 본 논문에서는 비접촉 트랜스포머의 파라메타 측정을 통하여 비접촉 트랜스포머의 등가화 회로를 구현하였고, 일반 비접촉 트랜스포머와 강압형 매칭 트랜스포머를 추가한 트랜스포머의 전압 이득과 입력 임피던스 특성을 해석하였다. 강압형 매칭 트랜스포머의 특성을 검증하기 위하여 30kW급 비접촉 전원장치를 제작하여 실험하였다.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.205-206
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• 2010

This paper presents a study on the efficiency of DC-DC converter to charge/discharge lithium battery. The losses of switching device, magnetic components, output capacitor, diode, and snubber circuit are analyzed by considering the charge/discharge characteristics of the converter. Based on the loss analyses, efficiency simulation in charging/discharging process are performed.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.189-190
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• 2018

본 논문에서는 유도전동기의 토크 리플 및 스위칭 손실 저감을 위해 전압변조기법인 공간벡터변조(Space Vector Pulse Width Modulation, SVPWM) 기법과 불연속전압변조(Discontinuous Pulse Width Modulation, DPWM) 기법을 혼합하여 사용하는 새로운 변조기법을 제안한다. 제안하는 방식은 지령전압이 최대인 부근에서 SVPWM 기법을 사용하며, 나머지 구간에서는 DPWM 기법을 적용한다. 전 구간 단일기법을 적용할 때와 비교하여 제안하는 방식은 토크 리플 및 스위칭 손실을 효율적으로 저감시킬 수 있으며 시뮬레이션을 통해 타당성을 검증한다.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1609-1618
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• 2015

DC microgrids are considered as prospective systems because of their easy connection of distributed energy resources (DERs) and electric vehicles (EVs), reduction of conversion loss between dc output sources and loads, lack of reactive power issues, etc. These features make them very suitable for future industrial and commercial buildings' power systems. In addition, the bipolar-type dc system structure is more popular, because it provides two voltage levels for different power converters and loads. To keep voltage balanced in such a dc system, a bidirectional dual buck-boost voltage balancer with direct coupling is introduced based on P-cell and N-cell concepts. This results in greatly enhanced system reliability thanks to no shoot-through problems and lower switching losses with the help of power MOSFETs. In order to increase system efficiency and reliability, a novel burst-mode control strategy is proposed for the dual buck-boost voltage balancer. The basic operating principle, the current relations, and a small-signal model of the voltage balancer are analyzed under the burst-mode control scheme in detail. Finally, simulation experiments are performed and a laboratory unit with a 5kW unbalanced ability is constructed to verify the viability of the bidirectional dual buck-boost voltage balancer under the proposed burst-mode control scheme in low-voltage bipolar-type dc microgrids.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.71-72
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• 2011

This paper presents a novel and direct dead time compensation method of the 3 phase inverter using space vector pulse width modulation(SVPWM) topology. In the turn on time calculation of the effective voltage, the dead time effect is directly compensated according to the current direction of the midium voltage reference. Since the turn on time of the effective voltage vector is affected by the dead time, the loss time is compensated to turn on time of the effective voltage vector. And the dead time is added to the calculated voltage vector switching times according to the current direction. For the more effective compensation, the direction of the midium phase current is considered by the practical direction and voltage drops in the power devices. The proposed method can compensate the dead time which is considered feedback error or direction of middle phase current without coordinate transform in added controller. The proposed dead time compensation scheme is verified by the computer simulation and experiments of 3 phase R L load.

• Journal of Power Electronics
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• v.9 no.2
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• pp.215-223
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• 2009

A design methodology for transformers including integrated and center-tapped structures for LLC resonant converters is proposed. In the LLC resonant converter, the resonant inductor in the primary side can be merged in the transformer as a leakage inductance. And, the absence of the secondary filter inductor creates low voltage stress on the secondary rectifiers and is cost-effective. A center-tapped structure of the transformer secondary side is widely used in commercial applications because of its higher efficiency and lower cost than full-bridge structures in the rectifying stages. However, this transformer structure has problems of resonance imbalance and transformer inefficiency caused by leakage inductance imbalance in the secondary side and the position of the air-gap in the transformer, respectively. In this paper, gain curves and soft-switching conditions are derived by first harmonic approximation (FHA) and operating circuit simulation. In addition, the effects of the transformer including integrated and center-tapped structures are analyzed by new FHA models and simulations to obtain an optimal design. Finally, the effects of the air-gap position are analyzed by an electromagnetic field simulator. The proposed analysis and design are verified by experimental results with a 385W LLC resonant converter.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.287-288
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• 2010

The Induction Heating equipment is widely used for steel plate heating in the surface treatment process of steel industries. In the case of thin steel plate, for high efficiency We need the high frequency induction heating equipment more than 100kHz. But it is difficult to realize the high frequency and high power at the same time. That's why most high frequency equipment more than 100kHz has been imported from advanced Manufacturer. This paper will describe the development of 100kHz/5MVA inverter module for 100kHz/20MVA induction heating. We used the LCL resonance topology and ZVS/ZCS switching technology. And we also developed the low loss gate drive board and plate busbar inverter stack. We proved the performance by various experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1562-1574
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• 1998

We, in this paper, have implemented T1, E1 and fractional E1 HDSL(High-bit-rate digital subscriber line) function over an ATM switching system. The maxi$\mu$ loop lengths for subscriber service and cell loss rates to meet the bit error rate of 10$^{-7}$ at transmission of 2B1Q HDSL data E1 rate over existing telephone copper wires in the presence of the significant impairments such as NEXT(Nearned crosstalk), impulse noise, power line noise and longitudinal over the CSAs environment consisting of 26 gauge and 25 gauge unloaded copper telephone lines has assessed. HDSL will intially be used to serve private-DS1, ISDN-BRA, and DLC feeders, later DS1 extension from optic fiber cable. We also present market provision for the HDSL.

• Journal of Magnetics
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• v.16 no.3
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• pp.246-252
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• 2011

A high-voltage power supply has been built for activation of the brain via stimulation using a Full Wave Cockroft-Walton Circuit (FWCW). A resonant half-bridge inverter was applied (with half plus/half minus DC voltage) through a bidirectional power transistor to a magnetic stimulation device with the capability of producing a variety of pulse forms. The energy obtained from the previous stage runs the transformer and FW-CW, and the current pulse coming from the pulse-forming circuit is transmitted to a stimulation coil device. In addition, the residual energy in each circuit will again generate stimulation pulses through the transformer. In particular, the bidirectional device modifies the control mode of the stimulation coil to which the current that exceeds the rated current is applied, consequently controlling the output voltage as a constant current mode. Since a serial resonant half-bridge has less switching loss and is able to reduce parasitic capacitance, a device, which can simultaneously change the charging voltage of the energy-storage condenser and the pulse repetition rate, could be implemented. Image processing of the brain activity was implemented using a graphical user interface (GUI) through a data mining technique (data mining) after measuring the vital signs separated from the frequencies of EEG and ECG spectra obtained from the pulse stimulation using a 90S8535 chip (AMTEL Corporation).